Method of suppressing noise in hermetic compressors

ABSTRACT

The method of attenuating the noise produced by an operating hermetic compressor unit by adding a foaming agent to the lubricating oil of the unit and agitating the oil during operation of the unit.

United States Patent 1191 Sanvordenker Feb. 19,1974

[54] METHOD OF SUPPRESSING NOISE IN 3,066,857 12/1962 McCloy 181/33 13UX HERMETIC COMPRESSORS 3,147,914 9/1964 Hatten et a1. 417/363 3,155,31211/1964 Douglas... 417/363 [75-] Inv ntor: s v Sanvordenker, Ann3,480,205 11 1969 Hatten 417/363 AlbOI', Mich. 3,614,384 10/1971Heitchue 417/312 [73] Assignee: Tecumseh Products Company, FOREIGNPATENTS OR APPLICATIONS i 188,228 11 1966 U.S.S.R. 181 33 B [22] Filed:Mar. 26, 1973 211 App]. 344 703 Primary Examiner-Richard B. WilkinsonAssistant Examiner.lohn F. Gonzales Attorney, Agent, or Firm-Barnes,Kisselle, Raisch & [52] US. Cl. 181/33 B, 181/33 C, 181/33 K, Ch t417/312 6 [51] Int. Cl. F04b 21/00 Field of Search..... 181/33 B, 33 C,33 K, 33 S, 57 S CT 623 The method of attenuatmg the nolse produced byan operating hermetic compressor unit by adding a foam- [56] ReferencesCited ing agent to the lubricating oil of the unit and agitating UNITEDSTATES PATENTS the oil during operation of the unit. 2,990,111 6/1961Bohn 417/363 X 15 Claims, N0 Drawings METHOD OF SUPPRESSING NOISE INHERMETIC COMPRESSORS This invention relates to the control of noise inmoving machinery and more particularly to a method of suppressing thenoise produced by a hermetic compressor unit.

A typical hermetic compressor unit has a gas compressor with a pistondriven by an electric motor totally enclosed in a sealed housing havinginlet and outlet couplings for a compressible refrigerant gas. Apredetermined amount of oil is received and retained-within the housingto lubricate the moving parts of the compressor and motor. The noiseproduced by the compressor unit is conventionally attenuated by asuction muffler, discharge muffler and other mechanical means such as aspring suspension to dampen vibration of the motor and compressor. Atypical hermetic compressor unit is shown in US. Heitchue Pat. No.3,614,384, issued Oct. 19, 1971, which has an agitator rotated in thelubricating oil to stir the oil. This agitation produces some bubbles inthe oil for the stated purpose of attenuating the noise produced by thehermetic compressor unit.

Objects of this invention are to provide a method of attenuating thenoise produced by an operating hermetic compressor unit which can bereadily adapted for conventional compressor designs; is compatible withexisting assembly and testing techniques and procedures formanufacturing hermetic compressors; can be commercially practiced withunskilled personnel; and economically and efficiently attenuates theoperating noise of hermetic compressors.

' In the method of this invention a foaming agent is added to thelubricating oil of a hermetic compressor to assist in generating andsustaining a froth or foam of fine bubbles which acts to absorb and thusattenuates the operating noise produced by the compressor unit. Thefoaming agent causes substantial quantities of a froth or foam of finebubbles to be rapidly created and sustained on the surface of thelubricating oil when it is agitated during operation of the hermeticcompressor unit. In existing hermetic compressor designs which do nothave a means for agitating the lubricating oil such an agitation meansshould be added for effective utilization of the method of thisinvention. In some conventional hermetic compressor designs there is aspecific mechanical member, such as a disc or a finger, for agitatingthe lubricating oil. In other designs, the connecting rod of thecompressor is partially submerged in the lubricating oil and issufficient by itself to agitate the oil.

A suitable foaming agent in accordance with the present invention is asolution commercially available from Dow Corning Co. of Midland, Mich.,sold under the trademark SILANE XZ-83076. This solution is believed tobe essentially 50 percent by weight of organosiloxane dissolved intoluene. Organosiloxanes have the following general chemical structure:

stances, including hydrogen, aryl and alkyl groups. These compounds canbe either linear or cross-linked polymers having molecular weights inthe range of 1,000 to 150,000. One of these simpler polymers is polydimethylsiloxane in which the Rs are methyl groups. More complexsilicone polymers can be formed by incorporating side chains of greatercomplexity, such as methyl ethyl polysiloxane and diethyl polysiloxane.Fluorine atoms can be substituted for some of the hydrogen atoms on theside chains to produce a more complex polymer, such as trifluoropropylmethyl polysiloxane; likewise, aromatic groups such as phenyl can beincorporated into these polymers.

The performance of these various compounds in a hermetic compressorshould be empirically checked, particularly for their foamingcapabilities and compatability with the refrigerant and refrigerationsystem in which they are used. The depth of the foam produced appears tobe dependent on operating conditions such as the pressure of therefrigerant, the amount of refrigerant dissolved in the lubricating oil,the extent of agitation of the oil, the temperature of the oil andrefrigerant in the casing of the hermetic compressor, and the specificfoaming agent and its concentration. The size of the bubbles of the foamappears to be dependent on the viscosity of the oil which varies withthe temperature of the hermetic compressor unit, the pressure of therefrigerant, the extent of agitation of the oil, and the specificfoaming agent and its concentration.

In general, the greater the depth or thickness of the foam and thesmaller the average diameter of its bubbles the greater the attenuationof the compressor unit operating noise. The depth of the foam isprimarily dependent on the concentration of the foaming agent in thelubricating oil and the extent of the agitation of the oil. Increasedconcentrations of the foaming agent and increased agitation produces athicker or deeper layer of foam on the surface of the oil.

In practice, the maximum permissible thickness or depth of the foam islimited by the design of the hermetic compressor unit. If the foam weredrawn into the suction inlet of the running compressor-which is withinthe casing of the hermetic unit, it could enter the compression chamberand damage the compressor. Hence, the spacing between the surface of thelubricating oil and the suction inlet of the compressor within thecasing, which is typically the inlet to the intake muffler, determinesthe maximum feasible depth of the foam.

Preferably, the foam should be at least about one inch in depth and adepth in the range of about 1% to 2% inches has provided substantialnoise attenuation.

The foam produces maximum attenuation at discrete frequencies believedto be dependent primarily on the average diameter of the bubbles. Sincethe most objectionable noise produced by hermetic compressor units is inrelatively narrow bands, the foam can be tuned for maximum attenuationof the noise of a particular compressor unit by varying the averagebubble diameter of the foam. The smaller the average bubble diameter themore stable the foam layer and the better the absorbtion of higherfrequency sounds above about 400 Hz.

The aforementioned organosiloxane foaming agents are soluble in variousaromatic hydrocarbons such as benzene, toluene and xylene; ketones suchas acetone and methylethyl ketone; alcohols such as isopropyl alcohol;and chlorinated hydrocarbons such as trichlorethylene,dichlorodifluoromethane (R-12) and monochlorodifluoromethane (R-22). Theuse of refrigerants R-12 and R-22 as solvents for organosiloxane foamingagents facilitates injecting the foaming agents into a refrigerationsystem utilizing a hermetic compressor unit. The foaming agent is firstdissolved in the R-12 or R-22 refrigerant and this solution is thencharged into such a refrigeration system as a final step in the assemblyof the complete system. Thus; all other manufacturing operations wouldbe unaffected if the foaming agent is dissolved in the refrigerant whichis charged into the system. This also allows existing equipment andprocedures for charging the refrigeration system to be used in injectingthe foaming agent and, thus, does not disturb or adversely affect theconventional steps and techniques in the assembly and testing of therefrigeration system.

Alternatively, the foaming agent may be mixed with a lubricating oil andthe mixture injected directly into the casing of the hermetic compressorunit. Controlling within close tolerances the ratio of foaming agent tooil is facilitated by dissolving the foaming agent in a volatile carrierwhich is compatible with and will evaporate from the lubricating oilsuch as acetone before mixing the foaming agent and carrier with thelubricating oil for injection of the mixture into the hermeticcompressor unit.

A suitable concentration by weight of an organosiloxane foaming agent isbelieved to be in the range of 100 to 3,000 parts per million (PPM) byweight ofthe lubricating oil. It is believed to be preferable to use aconcentration by weight of an organosiloxane foaming agent in the rangeof 100 to 1,000 PPM and approximately 150 to 800 PPM and particularly300 to 800 PPM has been found to satisfactorily substantially attenuatethe operating noise of a Tecumseh Products Co. hermetic compressor(Model No. AHL12) with a mechanical oil agitator. The organosiloxanefoaming agent added to the lubricating oil was SlLANE XZ- 83076 (withoutthe toluene solvent). The oil was a refrigeration grade minerallubricating oil having a vis- Cosity of approximately 150 SUS at 100 F.

The use of a foaming agent pursuant to the present invention decreasessubstantially the amount of time required to form a suitable foam orfroth for attenuating hermetic unit operating noise, greatly increasesthe quantity of the foam produced and stabilizes the foam by greatlyincreasing the average life of the bubbles. in fact, it is believed tobe a practical impossibility to produce'stable bubbles of sufficientdepth on the surface of the lubricating oil to significantly attenuatehermetic unit operating noise without using a foaming agent. Since thismethod only requires the addition of a foaming agent to the lubricatingoil and agitation thereof, it is economical and can be readily adaptedto conventional hermetic unit designs. The foaming agent can be mixedwith the refrigerant charge and injected into a hermetic compressor unitrefrigeration system along with the refrigerant and therefore the methodof this invention is compatible with conventional assembly and testingtechniques and can be economically practiced by unskilled labor.

1 claim:

l. A method of attenuating the noise produced by an operating hermeticcompressor unit having a means for agitating the lubricating oilreceived therein when the hermetic compressor unit is operating,comprising the steps of selecting a foaming agent compatible with theliquid refrigerant and lubricating oil employed in said compressor, andadding a predetermined quantity of said foaming agent to the lubricatingoil sufiicient to produce a quantity of foam within the hermeticcompressor unit when it is operating to attenuate the noise produced bythe operating hermetic compressor unit.

2. The method of claim 1 wherein the predetermined quantity of foamingagent produces a foam when the hermetic compressor unit is operatinghaving a depth in the range of l to 2 /2 inches.

3. The method of claim 1 wherein the predetermined quantity of foamingagent is in the range of to 1,000 parts per million by weight of thelubricating oil.

4. The method of claim 1 wherein the predetermined quantity of foamingagent is in the range of to 800 parts per million by weight of thelubricating oil.

5. The method of claim 1 wherein the predetermined quantity of foamingagent is in the range of 300 to 800 parts per million by weight of thelubricating oil.

6. The method of claim 1 wherein the foaming agent is an organosiloxane.

7. The method of claim 2 wherein the foaming agent is an organosiloxane.I

8. The method of claim 3 wherein the foaming agent is an organosiloxane.

9. The method of claim 1 wherein the foaming agent is an organosiloxanehaving hydrogen aryl or alkyl R groups.

10. The method of claim 1 wherein the foaming agent is added to thelubricating oil by being dissolved in a refrigerant which is chargedinto the refrigeration system in which the hermetic compressor unit isutilized.

11. The method of claim 2 wherein the foaming agent is added to thelubricating oil by being dissolved in a refrigerant which is chargedinto the refrigeration system in which the hermetic compressor unit isutilized.

12. The method of claim 6 wherein the foaming agent is added to thelubricating oil by being dissolved in a refrigerant which is chargedinto the refrigerationsysteni in which the hermetic compressor unit isutilized.

13. The method of claim 1 wherein the foaming agent is added directly tothe lubricating oil charged into the hermetic compressor unit.

14. The method of claim 2 wherein the foaming agent is added directly tothe lubricating oil charged into the hermetic compressor unit.

15. The method of claim 6 wherein the foaming agent is added directly tothe lubricating oil charged into the hermetic compressor unit.

2. The method of claim 1 wherein the predetermined quantity of foamingagent produces a foam when the hermetic compressor unit is operatinghaving a depth in the range of 1 to 2 1/2 inches.
 3. The method of claim1 wherein the predetermined quantity of foaming agent is in the range of100 to 1,000 parts per million by weight of the lubricating oil.
 4. Themethod of claim 1 wherein the predetermined quantity of foaming agent isin the range of 150 to 800 parts per million by weight of thelubricating oil.
 5. The method of claim 1 wherein the predeterminedquantity of foaming agent is in the range of 300 to 800 parts permillion by weight of the lubricating oil.
 6. The method of claim 1wherein the foaming agent is an organosiloxane.
 7. The method of claim 2wherein the foaming agent is an organosiloxane.
 8. The method of claim 3wherein the foaming agent is an organosiloxane.
 9. The method of claim 1wherein the foaming agent is an organosiloxane having hydrogen, aryl oralkyl ''''R'''' groups.
 10. The method of claim 1 wherein the foamingagent is added to the lubricating oil by being dissolved in arefrigerant which is charged into the refrigeration system in which thehermetic compressor unit is utilized.
 11. The method of claim 2 whereinthe foaming agent is added to the lubricating oil by being dissolved ina refrigerant which is charged into the refrigeration system in whichthe hermetic compressor unit is utilized.
 12. The method of claim 6wherein the foaming agent is added to the lubricating oil by beingdissolved in a refrigerant which is charged into the refrigerationsystem in which the hermetic compressor unit is utilized.
 13. The methodof claim 1 wherein the foaming agent is added directly to thelubricating oil charged into the hermetic compressor unit.
 14. Themethod of claim 2 wherein the foaming agent is added directly to thelubricating oil charged into the hermetic compressor unit.
 15. Themethod of claim 6 wherein the foaming agent is added directly to thelubricating oil charged into the hermetic compressor unit.